1. Field of the Invention
The present invention relates to a circuit for improving amplification and noise characteristics of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), and a frequency mixer, an amplifier and an oscillator using the circuit. More particularly, the present invention relates to a circuit for improving amplification and noise characteristics of a MOSFET which enables a MOSFET receiving and amplifying a signal to obtain a greater degree of amplification and a lower level of noise than when using a conventional circuit, and a frequency mixer, an amplifier and an oscillator using the circuit,
2. Description of the Related Art
Nowadays, wireless communication technology is developing at an accelerating pace, and communication standards are established according to the intended purpose of the technology. A current goal in the development of wireless communication technology is the incorporation of various communication standards into a single mobile communication device.
To provide simultaneous compatibility with various different standards, a Direct-Conversion method is widely used. However, to reduce signal distortion, a frequency mixer having excellent 1/f noise characteristics is required. The noise characteristics of the frequency mixer are very important because they have a considerable effect on overall 1/f noise in a transceiver, and 1/f noise causes serious signal distortion in a standard having a narrow frequency bandwidth.
Accordingly, additional inductors or capacitors are used to make filter circuits filter out noise-band signals and thereby improve noise characteristics. Also, a passive device, which has better noise characteristics than an active device, is used to reduce signal distortion. However, a frequency mixer formed of passive devices does not amplify a signal but rather attenuates it.